Leasing - Lease Balances (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Assets
Operating lease assets	$ 362	$ 391
Finance lease assets	47	38
Accumulated Amortization of Finance lease assets	(8)	(5)
Total leased assets	401	424
Liabilities
Operating lease liabilities, current	88	91
Finance lease liabilities, current	13	10
Operating lease liabilities, noncurrent	346	369
Finance lease liabilities, noncurrent	28	25
Total lease liabilities	$ 475	$ 495